Process of chlorinating saturated hydrocarbons



Patented June 24, 1930 UNITED STATES PATENT OFFICE RA LPH H. MOKEE AND CARROLL M. SALLS, OF NEW YORK, N. Y.

PROCESS OF CHLORIHATIN G SATURA QIED HYDRObARIBONS No Drawing. Application filed May 16,

This invention relates to chlorination of saturated hydrocarbons, such as methane, ethane, and the like, and more particularly to the chlorination of such substances by the use of sulfuryl chlorid.

The chlorination of saturated hydrocarbons, such as methane, to produce hydrochloric acid and other chlorinated products has heretofore been practiced by mixing chlorine with the product to be chlorinated. In general, there are formed in addition to the chlorinated product, larger or smaller amounts of carbon and other products due to the decomposition of the methane or other hydrocarbon. A material disadvantage of theprocess employing a hydrocarbon and chlorine is that the reaction is strongly exothermic and unless special precautions are taken, disastrous explosions are likely to occur. Such precautions generally consist in the provision of an excess of an inert gas such as steam or the use of an excess of methane which serves the same function as the inert gas. -The'use vof such diluent requires, excessively large apparatus, expensive and troublesome condensation methods and apparatus, and is further disadvantageous in that the diluent gas carries away certain amounts of the materials thus decreasing the yield.

It has heretofore been proposed to employ sulfuryl chlorid in the chlorination of -unsaturated hydrocarbons and also in the further chlorination of products already car-,

rying two atoms of chlorine. So far as we are aware, there has been no attempt to chlorinate saturated hydrocarbons, such as methane or ethane with sulfuryl chlorid.

The advantage of using sulfuryl'chlorid as a chlorinating agent for methane, ethane and other saturated hydrocarbons resides primarily in the fact that no great amount of heat isevolved when this material is used for chlorinating, The dissociation of the sulfuryl chlorid forms sulfur dioxid and chlorine, which then enters into the reaction with the hydrocarbon, and absorbs approximately two-thirds of the amount of heat that is evolved by the chlorination of the methane or other hydrocarbon. For this 1923. Serial No. 639,445.

reason, it is impossible to cause an explosion when methane or other hydrocarbon is mixed with sulfuryl'chlorid, no matter what proportion of the two materials is mixed. The use of sulfuryl chlorid thus siderable excess of sulfuryl chlorid. Due to the elimination of the use of the diluent gas, the necessity for excessively large apparatus is avoided.

By controlling the process, we can obtain a high yield of methyl chlorid and by in-JO creasing the amount of sulfuryl chlorid used, an excellent yield of one of the higher chlorinated products can be obtained. By proper choice ofproportions, it is practicable to obtain-a yield of 50 per cent. chloro- 7 form, CHCl and relatively small amounts of CH Cl, CHCl, and C01 In practicin prior processes where the hydrocarbon, and chlorine are mixed in the presence of a diluent gas, a yield of 25 per cent. chloroform was considered excellent operation. As stated, the dissociation of the sulfuryl chlorid absorbs nearly as much heat as is evolved, by the chlorination, but the excess heat evolved is suificient to keep the gas at the proper temperature without the application of outside heat after the operation has been started.

The action between sulfuryl chlorid and saturated hydrocarbons, such as methane, can be promoted by the presence of ionizing agents, such as sunlight, ultra-violet light, electric discharge, heat, certain catalytic agents of the type of metallic chlorids, and small amounts of catalysts such as the activated carbon described and claimed in the patent to Ralph H. McKee, No. 1,133,049. In the manufacture of chloroform or carbon tetrachlorid, the use of heat is preferred, al-

though sometimes heat in'conjunction with L,

-erably below 350 a small amount of a catalyst, such-.as the carbon referred to may be employed. In the manufacture of methyl chlorid, light or electric discharge is a more satisfactory activating agent than heat or a solid catalyst.

In the preferred practice of the process, a mixture of methane, a gas high in methane, or other hydrocarbon such as ethane or propane, with the desired amount of sulfuryl chlorid vapor, is passed through a filled vessel to give a turbulent flow to these vapors and thereby give evenness of temperature throughout the vessel, for example a tube filled with an inert material such as broken porcelain, and kept at a temperature of about 350 C. It is possible to employ lower temperatures in practicing the process but the rapidity of the reaction will be substantially reduced if a temperature consid- C. is. used. The speed of the reaction is such that the tube need be only of moderate-length, say, three feet. In one experiment, we employ 81 per cent. sulfuryl chlorid and 19 per cent. methane by volume. A gas was passed through the hot tube with complete reaction and Without explosion even though the gas rate was six times as fast as. any non-explosive methane, chlorine mixture could be run through the apparatus and approximately complete reaction be obtained. Small amounts of catalyst, such as the carbon mentioned above, may be placed on the porcelain or other filling arranged within the tube. The

.amounts of such catalytic agent must be relatively small or the dissociation of the sulfuryl chlorid will be too rapid, causing the formation of chlorine faster than it can be reacted with the methane, thus causing an accumulation of chlorine and the possibility of explosion. In the manufacture of methyl chlorid as the principal product, it is inadvisable to have any carbon or catalytic agent present. On the other hand, in manufacturing chloroform or the carbon tetrachlorid, the use of a small amount of carbon near the point where the mixture of gas enters the hot tube is advisable, although the presence of such catalytic agent is not essential. The process may easily be practiced so that less than 10 per cent. of the methane remains unacted upon and yet no carbon or other decomposition product is formed.

The gases issuing from the tube are cooled and the condensed chlorinated .products separated out and liquefied. The uncondensed products, chiefly methyl chlorid, unaffected methane, hydrogen chlorid and sulfur dioxid are washed with a small amount of water to remove the hydrogen chlorid as hydrochloric acid and the residual gases are compressed to liquafy the methyl chlorid and sulfur dioxid and permit the 'methane to pass on unchanged.

' employed in the Where the mixture contains a large amount of sulfur dioxid, a small amount of methane and methyl chlorid, it may be used to make sulfuryl chlorid by the process'disclosed in our copending application Serial No. 647,899, filed June 26, 1923. The hydrochloric acid recovered from the practice of the process is. of high purity and will find ready sale on the market.

As stated, natural gas high in methane may be employed in place of pure methane, and where chlorinated products of ethane are to be manufactured, a natural gas mixture high in ethane, such as the ethanefraction obtained when certain natural gas" is passed through the liquefication process, may be employed.

To obtain the, proper ratio of methane or other hydrocarbon and sulfuryl chlorid, various methods may be employed. The simplest method is to bubble the methane through the sulfuryl chlorid, the sulfuryl chlorid being kept at a predetermined tem-' perature. The higher the temperature of the body of sulfuryl chlorid, the larger the proportion of sulfuryl chlorid vapor to methane will be obtained. By choosing a proper temperature, the ratio between the two can be fixed at any point desired.

By (Zr-3 term chlorinating catalyst as claims is meant a catalyst which promotes the reaction between sulfuryl chlorid and saturated hydrocarbons to form chlorinated hydrocarbons. Illustrative examples of such chlorinating catalysts are metallic chlorids and activated carbon.

While we have described in detail the preferred practice of our process, it is to be understood that the details of procedure, and proportion of ingredients may be widely varied, and that known chemical equivalents may be employed in place of the ma terials mentioned, without departing from the spirit of the invention or the scope of the subjoined claims.

We claim:

1. The process of chlorinating saturated hydrocarbons which comprises treating such hydrocarbons with sulfuryl chlorid in the presence of an ionizing influence.

2. The process of chlorinating methane which comprises treating it with sulfuryl chlorid in the presence of an ionizing influence.

3. The process of" chlorinating saturated hydrocarbons which comprises treating such hydrocarbons with sulfuryl chlorid in the presence of the ionizing influence of heat.

4. The process of chlorinating saturated hydrocarbons which comprises treating such hydrocarbons with sulfuryl chlorid in the presence of a chlorinating catalyst.

5. The process of chlorinating methane which comprises treating it with sulfuryl chlorid in the presence of a chlorinating catalyst. 6. The process of chlorinating saturated hydrocarbons which comprises passing. a mixture of the vapor of such hydrocarbons and sulfuryl chlorid through a filled vessel at a temperature of substantially 350 C. 1 7. The process of chlorinating methane which comprises passing a' mixture of the m vapor of methane and sulfuryl chlorid through a filled vessel at a temperature of substantially 350 C.

8. The process of chlorinating methane which comprises passing a mixture of methane vapor and sulfuryl chlorid over activated carbon and subjecting it to the ionizing influence of heat.

9. The process of chlorinating saturated hydrocarbons which comprises passing amixture of the vapor of such hydrocarbons and sulfuryl chlorid through a filledvessel at a temperature of substantially 350 C. in thepresence of a chlorinating catalyst.

10. The process of chlorinating methane which comprises passing a mixture of the vapor. of methane and sulfuryl chlorid through a filled vessel at a temperature of substantially 350 C. in the presence of a chlorinating catalyst. so In testimony whereof, we afiix our signatures. v

RALPH'H. MoKEE.

CARROLL M. SALLS. 

